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DIY air ioniser

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Dr. Dark Current

Tue Jul 29 2008, 10:04AM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

I was searching the net for air ionisers but I really didn't find much (only complete air purifier products).

As I understand it these are just simple negative DC high voltage generators right?

Another question I have is about the output electrode assembly. Is it just a needle (needles) pointing in free air or is there a ground nearby, and would pointing a fan at the electrode improve efficiency?

And finally, don't these generate dangerous gases (ozone)?

Thanks for any thoughts on this.

-J.M.

Coronafix

Tue Jul 29 2008, 10:52AM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

As I understand it, the finer the needle tip, the smaller the ions generated off the end.

Mates

Tue Jul 29 2008, 11:32AM

Registered Member #1025 Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566

Ozone is unwanted and best ionizers do not produce it (or active carbon filters are used).

I know how looks the gut of electrostatic particle remover which is used in aseptic boxes (for cell culturing). Basically it is a long wire (cathode) creating something like a fence (distances are cca 3 cm). Below the wire is a 3-4cm layer of wadding made of some polycarbonate (PP?) and below the wadding is a metal mesh (anode). Air is pumped through this filter and there is one more below containing active carbon. The whole system is based on fly-back like transformer, but I have no idea what is the final voltage (must be over 10KV). The freq is around 15 KHz because I can hear the whistling...

Dr. SSTC

Tue Jul 29 2008, 11:45AM

Registered Member #1407 Joined: Fri Mar 21 2008, 07:09AM
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Posts: 222

have a look at his website

there is lots of good little things there too

Dr. Dark Current

Tue Jul 29 2008, 12:44PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

jovica93 wrote ...

have a look at his website

there is lots of good little things there too

thanks! I think I will build a flyback powered thing with ~-15kV output with moderate current limiting (so it only doesn't kill me when i touch it accidentaly) and point a fan on the needles.

Should generate loads of negative ions (and not much ozone I hope) and I can start evaluating if these things make any difference in air quality

Marko

Tue Jul 29 2008, 01:57PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Most of on those 'air ionizers' looks like BS. Search for ''electrostatic dust precipitator'' , that should lead you to right way.

These needle 'ionizers' will produce ozone, which I think will be only feelable effect. It will charge dust and air molecules, but it must be noted that charged particles are repelled of the needle and attracted to ground due to their charge, and will flow in a steady wind. (pretty much like a lifter). I don't see a benefit of dust being attracted to ground - as soon as it discharges small movements of air can make it airborne again.

Dust precipitators correct this by using large metal plates as anodes which collect and trap dust. They of course need to be frequently cleaned.

There is no way negative ions can be of any benefit to humans on their own, because as soon they come in contact with anything conductive they will effectively stop existing, and charge will be either led to ground or just distributed over the body.

And even if someone was touching the needle this too would be tiny considering one can typically charge himself to far higher voltages by walking on a PVC floor.

Marko

quicksilver

Wed Jul 30 2008, 01:24PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

Here is a source for the modules

in either 12Vdc or 120Vac : 7.5K or 12.5K. They are potted but of fairly high quality. I can run a little centimeter arc off of the 12Vdc unit but it's weak and thin.

I made a little ionizer for the kitchen to see if it had any effect on cooking smells and I think I may.....but I wouldn't bet the farm on it.

flannelhead

Wed Jul 30 2008, 02:40PM

Registered Member #952 Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388

I once made a small 'air ionizer' using disposable camera parts... Real fun to play with, but nothing too useful.

It consisted of a disposable camera transformer and a CW multiplier.

Dr. Dark Current

Sat Aug 16 2008, 07:39PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

I finally got back to this and made a generator test lashup.
It makes approx. -15kV DC smoothed with HV cap, which is fed to an output electrode assembly with 6 nails in a piece of wood.
As it operates, I can hear the corona hissing and tips of the nails glowing in the dark, which by itself is pretty cool

However I'm concerned about ozone production, will there be generated enough ozone to present any health dangers?

Bjørn

Sat Aug 16 2008, 09:22PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

In general ozone becomes irritating before it reaches a dangerous concentration. So if you don't notice it you are quite safe. That you can hear the discharge is often a sign of significant ozone production and it might generate enough to be a problem. Air ionisers should be quiet.

Ozone can make you sick as a dog in just a few minutes and it is not a very pleasant experience. So if you feel any of the symptoms it is a good idea to open a window.

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